9 V difference between ground and ground

[Arrandir]

My windlass stopped working a couple of days ago. Not so strange when I measured the voltage between the terminals, less than 4 V.
The negative windlasscable is comnected to the generators ground. I have not changed anything on it after I bought the boat more than one year ago. The ground had no cable attached, except to the windlass. Should it not be a cable attached to negative terminal to the batteries? The difference between battery ground and generator ground was 9 V, that was the reason to the low voltage at the windlass..
I suppose I just can move the cable to another groundpoint, but something must be wrong, somethimg that might become a problem later. Any ideas of what have happened and how to fix it?

[old frog]

Originally Posted by Arrandir

-The negative windlass cable is comnected to the generators ground.
-The ground had no cable attached, except to the windlass.
-The difference between battery ground and generator ground was 9 V, that was the reason to the low voltage at the windlass..
-I suppose I just can move the cable to another groundpoint, but something must be wrong, somethimg that might become a problem later.

Your questions suggest that you do not have a solid grasp of recreational marine wiring practices.

I am understanding from your description that: The deck mounted windlass is connected to the auxiliary generator VAC earth ground point and that connection for the auxiliary generator earth ground only to the windlass DC negative connection.

If that is correct. I strongly, strongly suggest:
1. You do not use the generator and/or shore power.
2. Immediately disconnect the boat from shore power if connect to shore power.
3. Retain an experienced recreational marine electrician with current ABYC electrical and corrosion certifications to inspect and service your boat's entire electrical systems.
4. It would probably also be wise to also discontinue use of DC systems until they are inspected & serviced if needed.

Hopefully, I am misunderstanding what you wrote and that you are simply confusing the terms generator ground (which I am interpreting as the generators' AC earth ground) and the DC negative.

Seriously, this could be a very serious & dangerous situation. Faults in an AC systems ground + a fault in the system can be very, very dangerous.

9VDC difference within the DC negative side indicates a serious DC problem as well (both from possible high resistance connections &/or stray current corrosion).

[Arrandir]

Thanks for the reply. It is not AC. I will start to look for stray currents as soon as possible. Until then, the startbattery will not be connected.
I forgot to mention that the there is only difference when the starterbattery is connected, not the housebank.

[old frog]

Good. Just verify that the generator earth ground is grounded properly. Google the ABYC or NFPA 302 standards. (Personally, I think the NFPA 302 text is easier to read while the ABYC diagrams are at tad clearer.)

Something is definitely wrong the DC ground. Again, google the NFPA & ABYC standards for DC systems. Pay attention to the various busses (DC negative, AC earth ground & bonding) and the requirement for the duplicate negative battery cable between starting motors & genset(s). With a clear picture of what is supposed to be there, it is easier to see what might be missing & wrong.

Is reads as if you have isolated the circuit & power source with the problem. Usually, in these type situations, there are several things wrong. 1+ faults combined with 1+ high resistance connection. If you are not familiar with voltage drop tests, google it. It is an easy test once understood & often the quickest method to identify a high resistance connection. ( https://www.hagerty.com/articles-vid...g-voltage-drop )

Good luck with it.

[roland stockham]

I agree with Old Frog. The fact that the windlass is grounded to the generator generator suggests that it was installed by someone who did not know what they are doing. The worry is 'what else did they do'. I would want the boat wiring inspected by someone competent to check there is nothing else amiss.

Grounding can get quite complex but at the simplest level the ground wire is a safety connection from all the A/C devices and outlets that runs back to the source of generation. If this is an on board generator (or inverter) that is the ground point. If the source of power is shore power then everything is grounded via the shore power cable to the onshore generator and, as a backup via the boats A/C earth point (in case of problems with ground connections in the marina wiring which are common!.
D/C does not have a 'ground', it has a Neg. This is the neg battery terminal. The DC neg does not need to be connected to an external point however some regs call for a connection between DC neg and A/C ground so that in the event of a fault in the A/C that leeks current into the D/C system that current has a second path to earth.

The reason for the concern is that if they ground is not set up right and you have an a/c fault the only ground path available may be you.... Even at 120v A/C is lethal in boats as salt water is such a good conductor,

[old frog]

This is a good of a place as any to bring mention Lucas Ritz (RIP) and his father Kevin's mission of In Water Shock Hazard. If you have ever heard Kevin speak on the subject, it is something you will never forget. This issue is not to be taken lightly. It is something all boats and those that use the water near boats & marinas need to be aware of.

https://www.youtube.com/watch?v=eVty...&frags=pl%2Cwn

https://www.nfpa.org/~/media/1566859...44036C59F4.pdf

[saillr]

You have a bad connection likely due to corrosion somewhere in the 12V supply to the windlass. The negative should go direct to the battery or a solid connection that goes direct to the battery in a DC windlass. If you have up/down switches (as most do these days) you will have a solenoid that controls the flow to the windlass. Check for voltage at all points both in the ground line and the positive line. Most cable feeds are large and the connectors crimped. Check each connector and the solenoids connections for voltage drop. It will be there somewhere.

[Cadence]

I'm not sure I got what was powering the windless? I would hazard a guess that all of your batteries have lost a common ground be it engine start, gen, start and house. Probably corrosion someplace in the ground connections. You may want to check your zincs as a precaution.

[hellosailor]

It sounds like the PO didn't know how to do wiring, but may have actually done this intentionally, to make sure the windlass could only be used on generator power--and not on battery power. That's the only rationale that I can think of, and I've heard stranger things.

In any case, the fix will include properly rewiring the windlass to the ship's power, by any of the usual choices. You'll need to look at the options and start ordering some cable, at the least.

[Arrandir]

I daily use three languages, I think it became an error in my first post due to this. I ment the alternator, not generator. DC negative, not ground. Anyway, there is difference between alternators negative and the place on the engine where the negative cable to batteries is connected (not start engine).
I will check the zink tomorow, so far no results in voltage drop.

I have suppposed that earlier owners made it right. The one who had the boat from 2005 was a mechanic.

[Crusty Joker]

Item one.
Do not assume.
Know. There is no substitute for knowing exactly what is and is not going on here.
We have a boat owner that might just fry himself trying to figure things out in three languages.
All DC grounds on a standard 12 or 24 volt DC boat system
need to be connected together. All metal through hulls need to be connected and in good physical and electrical contact to a solid copper wire that is connected to the negative terminal of the battery. All heavy equipment needs to be connected to the negative terminal of the battery system and that includes the engine, windlass, generator, shaft and rudder and post, and all metal fixtures including davits, and swim step supports.
Shore ground wire is excluded or isolated at the connector at the boat end of the cable. Inside this fixture where the shore power connects to the boat, the boat bonding system or negative terminal of the battery is the boat ground and AC ground. Metal in salt water is a better ground than a copper rod buried in earth.
Get an electrician that knows boats and AC/DC mixed panels and logic circuits and can draw out your system.
Sounds like someone disconnected an important ground from battery to windlass or the windlass was wired to operate from another source.
Long windlass wires have caused fires and burned boats. There is a big difference between running a 12 volt motor with no load, and putting 350- 750 AMPs through a #12 or #10 wire when the windlass is bringing in chain and anchor! That wire becomes a fuse link. It will burn up and catch things on fire. That is why you need to use a heavy cable sized for the load and distance from energy source to windlass, with proper size and accessible breaker / fuse link.

Mechanics are not GOD. We did not invent nature. We use its rules and regulations or suffer consequences like everyone else. Even God follows his own rules. I am lucky in that I learned from some of God's angels. Some of the names in the text book. That was my only hope to learn anything electrical. And survive. Every day of my life I am thankful to my teachers and more and more, I am respectful and dependent on this forum. Most of the lady contributors know more than I do anymore! Thanks everyone!
bfh aka Crusty Joker

[Cadence]

Originally Posted by Crusty Joker

Item one.
Do not assume.
Know. There is no substitute for knowing exactly what is and is not going on here.
We have a boat owner that might just fry himself trying to figure things out in three languages.
All DC grounds on a standard 12 or 24 volt DC boat system
need to be connected together. All metal through hulls need to be connected and in good physical and electrical contact to a solid copper wire that is connected to the negative terminal of the battery. All heavy equipment needs to be connected to the negative terminal of the battery system and that includes the engine, windlass, generator, shaft and rudder and post, and all metal fixtures including davits, and swim step supports.
Shore ground wire is excluded or isolated at the connector at the boat end of the cable. Inside this fixture where the shore power connects to the boat, the boat bonding system or negative terminal of the battery is the boat ground and AC ground. Metal in salt water is a better ground than a copper rod buried in earth.
Get an electrician that knows boats and AC/DC mixed panels and logic circuits and can draw out your system.
Sounds like someone disconnected an important ground from battery to windlass or the windlass was wired to operate from another source.
Long windlass wires have caused fires and burned boats. There is a big difference between running a 12 volt motor with no load, and putting 350- 750 AMPs through a #12 or #10 wire when the windlass is bringing in chain and anchor! That wire becomes a fuse link. It will burn up and catch things on fire. That is why you need to use a heavy cable sized for the load and distance from energy source to windlass, with proper size and accessible breaker / fuse link.

Mechanics are not GOD. We did not invent nature. We use its rules and regulations or suffer consequences like everyone else. Even God follows his own rules. I am lucky in that I learned from some of God's angels. Some of the names in the text book. That was my only hope to learn anything electrical. And survive. Every day of my life I am thankful to my teachers and more and more, I am respectful and dependent on this forum. Most of the lady contributors know more than I do anymore! Thanks everyone!
bfh aka Crusty Joker

Why don't we make something that worked and has corrosion in the ground circuit as difficult as possible? Lets rewire the entire boat.

[hzcruiser]

Originally Posted by Arrandir

My windlass stopped working a couple of days ago. Not so strange when I measured the voltage between the terminals, less than 4 V.
The negative windlasscable is comnected to the generators ground. I have not changed anything on it after I bought the boat more than one year ago. The ground had no cable attached, except to the windlass. Should it not be a cable attached to negative terminal to the batteries? The difference between battery ground and generator ground was 9 V, that was the reason to the low voltage at the windlass..
I suppose I just can move the cable to another groundpoint, but something must be wrong, somethimg that might become a problem later. Any ideas of what have happened and how to fix it?

Hello Arrandir,

yes, I'm afraid your post is a bit confusing and thrown together in the order it popped up in your head? It seems as if you do have some knowledge of electrosity, though, being able to measure the voltage on the windless and knowing that about 4 V is not going to run the windless.

So to recap:

1: there is no AC involved here.
2: the only wire from the negative windless post is to the alternator negative post?

That would be a rather unusual setup, especially since most alternators don't have a negative post but use the engine block as negative. From there it goes back to the starter battery possibly via the starter motor housing.

I then wonder where the positive cable from the windless is going to? First to some switch to turn it on, of course, but then? Does it go back to the starter battery or to the alternator?

Also, is there a proper fuse in line on one of these cables?

Taking a step back, since "everything worked" until recently, and assuming there are no gremlins on your boat ripping out cables, it sounds like there is a point where corrosion is now bad enough to cause a significant voltage drop.

Re-reading your follow-up post about the house and starter battery bank, it now seems to be clear that you do indeed have two "grounds", one for the starter battery -> starter motor -> alternator/engine block -> windless circuit and one for the house bank.


[ BTW, that is exactly what I have, as well. Only my boat is steel and I can't avoid having the engine, starter motor, alternator and starter battery minus/ground all connected to the hull.

The house bank and all the house consumers including the windless are then wired with their own positive and negative cables. This means you would need a switch that connects both, plus and minus to charge your house bank from the alternator. ]

If that's the case you can ignore any potential difference (=voltage) between your house ground and the engine ground (for now), if that's what you measured?
The corrosion or loose connection would then be in either the positive or the negative wire run from the alternator to the windless. Do you have a foot switch on the deck to weigh anchor? That would be the first candidate to check for corrosion and wear (inside the switch, check the contact plates) because of the heavy arc'ing that's happening. That was the case with my foot switch, I had to replace the whole thing a few years ago.


Maybe some pics or a diagram would help as well...